1. Field of Invention
The present invention relates to a distal protection and delivery system that is placed using a guidewire in a tubular member of the human body that has a lesion or injury that requires diagnosis or therapy without allowing emboli to be released downstream. More specifically the invention relates to an intravascular system that is placed percutaneously into a blood vessel of the body that has a lesion to be treated by angioplasty, stent placement, atherectomy, thrombectomy, or other therapy, or diagnosis. The blood vessel to be treated can include the coronary, carotid, femoral, popliteal, or other vessel having a vascular lesion that requires interventional treatment. During treatment of such blood vessels, embolic debris can be embolized downstream causing blockage to distal capillary beds and arterioles. This vascular blockage results in reduced tissue perfusion and compromised tissue function. Placement of a distal protection device downstream of the treatment site can allow emboli to be collected and removed from the body rather than causing embolic injury. The distal protection and delivery system of the present invention includes a guidewire that can navigate tortuous blood vessel to reach the vessel lesion as easily as other standard prior art guidewires. The system also includes a filter assembly that is not attached to the guidewire and therefore can be delivered with an introducer to a site distal to the vessel lesion separately from the guidewire.
2. Description of Prior Art
Distal protection devices have been used in tubular vessels of the body including arteries and veins in order to prevent emboli such as thrombi, plaque, and other embolic debris from drifting downstream and causing distal tissue injury. Most distal protection devices have filters that are attached directly to the distal portion of a guidewire or to a portion of a catheter. Filter devices can sometimes be used during surgery, during percutaneous interventional procedures, and also filters can be implanted permanently into the body. The device of the present invention is intended for use during angioplasty or other interventional use.
Distal protection devices having a filter attached to a guidewire include the device of Tsugita (U.S. Pat. No. 5,910,154), Kerr (U.S. Pat. No. 5,941,896), Ruiz (U.S. Pat. No. 5,928,261), Reger (U.S. Pat. No. 5,160,342), and Ginsburg (U.S. Pat. No. 4,873,978). Tsugita describes a filter apparatus for treating stenosed blood vessels. The guidewire has a filter attached to it for capturing loose embolic material. The filter has an expansion frame having a filter mesh attached to it. One major difficulty with this type of device is that the guidewire cannot traverse a tortuous pathway in a blood vessel with a filter attached and with a holding tube surrounding the filter to hold it in the smaller diameter configuration. The filter along with the holding tube are very stiff and will restrict the ability of the guidewire from making tight turns into small vessels. Kerr describes a conically shaped filter with a porous fabric or a fine fiber mesh. Emboli from an angioplasty procedure are trapped by the filter and connecting loops can be drawn together to hold the emboli. This device shares similar disadvantages to the device of Tsugita. Ruiz describes a removable vascular filter and apparatus that is expanded within the vessel and held in place by a coiled-sheet stent portion with a magnetic band. When the coiled-sheet stent portion is released within the blood vessel, it uncoils to engage a wall of the vessel and deploys the filter element across the flow path. This device would be very stiff due to its configuration and would have much difficulty traversing a tortuous vascular pathway. Reger describes a filter device for use during angioplasty or atherectomy having a filter assembly mounted on a flexible catheter or guidewire. The device contains a filter element such as a polyester cloth that can be closed using a drawstring. A rotating motion can be used to twist the stocking filter to aid in containing the embolic material. This device has a filter permanently attached to the guidewire and will therefore have much greater stiffness than a standard guidewire, thereby limiting its access to smaller vessels and vessels with difficult conformation. Ginsburg describes a catheter device with a filter at the end of a wire that is entered percutaneously from the downstream side of the lesion. This device is extremely limited by virtue of reduced or nonexistent access to the blood vessel in most cases downstream of the lesion. This device also shares the difficulties associated with having a permanently attached filter that will result in a stiff device.
Lefebvre describes in U.S. Pat. No. 5,810,874 a filter catheter that is intended for long periods of use. It has strips that form a filter that can be detached from the connecting means into a blood vessel. This device is not intended to capture and remove emboli, however. This device depends upon the natural thrombolytic mechanisms of the body to break down thrombus or emboli that have been collected by the filter.
In U.S. Pat. No. 5,846,260 by Maahs a modular blood filter device is described that can be introduced into a blood vessel. The device consists of an arterial cannula with a modular filter device. The frame may be expanded to an enlarged condition to capture embolic material in a mesh filter and collapsed to a contracted condition and removed from the vessel. The device appears to be very mechanical, stiff, and cumbersome, and would not have efficient application to interventional procedures in vessels that require a soft and flexible catheter.
Barbut describes a device and method for filtering emboli generated from a blood oxygenator in U.S. Pat. No. 5,769,816. The device has an insertion tube, an umbrella frame for positioning and maintaining a mesh filter in position, and a means for opening the umbrella frame. An inflatable balloon is attached to the mesh filter. This device is much too stiff and awkward to be used in a percutaneous interventional application that requires a flexible catheter and guidewire.
Gewertz (U.S. Pat. No. 4,969,891) describes a filter member attached to a wire member that is intended to enter the jugular vein and be advanced to the vena cava. The device is easily replaceable and removable at the end of the procedure. This device does not retrieve the thromboemboli but rather depends upon the body to break down the emboli. This is a temporary filter to remove large clots in the venous system. It could not work to retrieve emboli in an interventional procedure.
Molgaard-Nielson (U.S. Pat. No. 4,619,246) and Rasmussen (U.S. Pat. No. 5,133,733) describe filters that are placed into a blood vessel such as a vein to block emboli. The device of Molgaard-Nielson is a wire filter mesh attached to a wire and could be implanted and then moved within one week. Emboli that have been trapped are not intended to be removed from the vasculature. Rasmussen describes a filter that is normally deployed in the vena cava via a catheter in a collapsed form and expands outward to capture emboli. This device is intended for implant and does not provide for means to remove any collected emboli.
The present distal protection and delivery system overcomes the disadvantages of other prior art distal protection devices. The present distal protection and delivery system does not have the filter assembly attached directly to the guidewire during insertion of the guidewire as it is with other prior art systems. Other prior art systems have attached their filter assembly directly to the guidewire and have compromised their ability to extend through difficult turns and reach some lesion sites due to the stiffness associated with the filter assembly and the introducer catheter. One component of the distal protection and delivery system of the present invention is a guidewire, another is a distal introducer, and another is a filter assembly. The guidewire component of the present invention can be formed with flexibility, trackability, and other structural features that are the same as other standard guidewires used for normal interventional procedures. Since the filter assembly is not permanently attached to the guidewire, the guidewire component of the present invention can extend through tortuous paths to reach and cross difficult lesions that require interventional treatment. Once the guidewire component of the present invention has reached the site of the lesion, an introducer catheter carrying a filter assembly in a nondeployed state is able to follow over the body or trunk of the guidewire to reach and cross the lesion. The filter assembly is then latched to a protrusion or ferrule located on the guidewire by an ejector latch on the filter assembly. The filter assembly is therein positioned on the guidewire and can be deployed into the blood vessel by advancing the guidewire distally or retracting the introducer proximally. The filter assembly undergoes an expansion from a smaller diameter of the introducer to the larger diameter of the blood vessel. A porous filter material located on a portion of the filter assembly serves to allow blood flow through the filter but restricts the flow of embolic material from passing distal to the filter assembly.
In one embodiment a latching of the filter assembly to the guidewire results in maintaining the positioning of the filter assembly with respect to the guidewire during deployment of the filter assembly and any axial movement of the guidewire can result in some movement of the filter assembly. In another embodiment latching of the filter assembly to the guidewire is only temporary (as long as) while the filter assembly is not deployed from the distal introducer. The filter assembly of this embodiment is unlatched upon deployment and the guidewire is free to move distally with respect to the filter assembly without affecting positioning of the filter assembly. In yet another embodiment an ejector tube is used to eject the filter assembly out of the introducer rather than using an ejector latch. In this embodiment the guidewire is free to move with respect to the filter assembly following deployment of the filter assembly into the blood vessel.
The filter material can be formed from a polymeric material or composite material that has holes of appropriate size to filter embolic debris drilled in it. Embolic debris can substantially range in size from about 10-1000 micrometers and can have the shape of flat plates or discs. Some embolic debris of a smaller diameter or thickness may be allowed to pass through the filter along with blood cellular elements which range in diameter from approximately 1-15 micrometers. Filter material can also be formed from cloth-like material such a woven polymeric, metallic, or composite materials. Other methods of forming the porous material include electrostatic spraying and extrusion of small polymeric filaments held together by solvent or thermal melt at crossover points. Another method of forming a porous thin filter material includes expanded polymeric material such as expanded polytetrafluoroethylene and expanded polypropylene.
With the filter assembly positioned in the blood vessel distal to the lesion the introducer can be removed from the blood vessel. An angioplasty catheter can then be introduced over the guidewire of the present invention. The present invention is primarily intended for and can be positioned in a coronary artery, a carotid artery, other neurovascular artery, a peripheral artery of the leg, or any other blood vessel that requires interventional treatment such as angioplasty and would benefit by a distal protection filter. Other therapeutic and diagnostic devices can also be advanced over the guidewire of the present invention such as stent delivery catheters, atherectomy catheters, thrombectomy catheters, angiography catheters, and other interventional catheters. During the use of such interventional catheters emboli are often generated from the plaque and deposit found on the vessel wall. These emboli can drift downstream if a distal protection device of the present invention is not positioned to capture the emboli distal to the lesion. Such emboli can block distal capillary beds and arterioles resulting in reduced tissue perfusion distal to the lesion. The presence of the filter assembly of the present invention will capture this embolic debris and allow the filter and embolic debris to be removed using the introducer of the present invention. In addition to use in the blood vessels of the body, the present invention could also be used in other tubular vessels of the body such as those found in the ureter, bladder, gall bladder, kidney, and other tubular vessels of the body.
Following the completion of all primary or adjunctive therapeutic or diagnostic procedures, the therapeutic or diagnostic catheters can be removed or retracted over the guidewire of the present invention. The introducer catheter can then be readvanced over the guidewire to a site of the filter assembly distal to the lesion in order to retrieve the filter assembly. The guidewire can be retracted proximally such that the locking mechanism of the guidewire interacts with a stop mechanism on the filter assembly and pulls the filter assembly proximally either partially or completely into the introducer catheter. The distal protection system of the present invention is then removed from the vasculature with the filter assembly containing the embolic debris.
The filter assembly of the present invention can have many conformations without changing the intent of the invention. In one embodiment the filter assembly is formed from Nitinol or other shape memory material support members that extend from a proximal band to a distal band that slidingly moves with respect to the guidewire. This embodiment of the filter assembly can be formed from a single shape memory or elastic metal tubular member that has been slotted by laser or other mechanical or chemical method to form the support members. Alternately, the filter assembly can be formed of wires made of an elastic or shape memory material that are attached to a proximal or distal band. The filter assembly is unable to escape distally from the guidewire due to a stop mechanism on the filter assembly that interfaces with a locking mechanism on the guidewire. The porous filter material is attached to the distal portion of these support members which hold the filter material outward against the vessel wall to prevent leakage of embolic debris around the perimeter of the filter or through the filter.
In another embodiment of the filter assembly a zig zag expandable ring is attached via support members to a proximal band. A porous filter material is attached to the distal end of the ring and forms a wind-sock form of embolic filter. In yet another embodiment for a filter assembly a Nitinol lasso is formed with a wind-sock like filter attached to it. Upon ejecting the filter assembly from the introducer, Nitinol wire is fed out to the loop allowing it to enlarge and come into contact with the vessel wall. In still yet another embodiment of the filter assembly two Nitinol wires connect together distally to form a single loop that is attached to a wind-sock like embolic filter. Upon ejection of the loop into the blood vessel the two Nitinol wires form an enlarged loop approximating the diameter of the blood vessel.
The distal protection and delivery system of the present invention can be operated as an over-the-wire system wherein the introducer catheter follows over a guidewire over substantially the entire length of the introducer catheter. In order to remove an over-the-wire introducer catheter while maintaining the position of the guidewire and filter assembly within the vessel distal to the lesion, an exchange length guidewire of the present invention of about 260-320 cm can be used. A long exchange length guidewire allows other over-the-wire therapeutic or diagnostic catheters to be placed over the guidewire and delivered to the site of the lesion and to remove them following their use. Alternately, an over-the-wire distal protection and delivery system having an over-the-wire introducer catheter containing the filter assembly can be initially loaded onto a shorter more standard length expandable guidewire of approximately 170-200 cm. This expandable guidewire can later be expanded if necessary to allow exchanges of over-the-wire catheters. The introducer and guidewire can be delivered percutaneously to a site that is proximal to the vascular lesion to be treated. For example, in treating a coronary lesion, the introducer and guidewire can be advanced through a guide catheter to a position near the coronary ostium. The guidewire can then be advanced across the lesion while the introducer catheter remains within the guide catheter. The distal introducer containing the filter assembly is then advanced over the guidewire to a position distal to the lesion. Deployment of the filter assembly is the same as described earlier. The guidewire is retracted proximally to latch the ejector latch of the filter assembly with the ferrule or locking mechanism located on the guidewire. The introducer is then withdrawn while maintaining the position of the guidewire to release the filter assembly and allow it to expand out to the diameter of the blood vessel. In order to remove the over-the-wire introducer from the vasculature without moving the distal end of the guidewire, a proximal extension guidewire of the present invention is attached by crimping or other mechanism to the proximal end of the expandable guidewire. This forms the expandable guidewire into an exchange length guidewire. Other catheters can be introduced over the extended guidewire and advanced to the lesion and can be removed from the vasculature over this guidewire. Following completion of interventional treatment the introducer catheter is reintroduced into the blood vessel the filter assembly is retracted into the distal introducer either partly or completely in a manner such that the filter membrane containing the embolic debris is retained within the distal introducer. The distal introducer, filter assembly, and guidewire can be removed from the vasculature along with the embolic debris that has been collected in the filter assembly.
Another embodiment of the distal protection and delivery system has an introducer catheter that is designed for rapid exchange with a distal introducer positioned at the distal end. In this embodiment the guidewire of the present invention can be of a standard length of approximately 170-200 cm and the introducer catheter provides passage for the guidewire through an intermediate portion of the catheter and the distal introducer. The filter assembly is positioned in the distal portion of the introducer and is deployed and retrieved back into the distal introducer in a manner similar to the other embodiments already described. The introducer catheter can be removed from the standard length guidewire while maintaining the position of the distal end of the guidewire in position across the lesion. Other rapid exchange therapeutic or diagnostic catheters can be delivered to the site of the lesion over the standard length guidewire of the present invention. The filter assembly can be removed from the vasculature using the initial rapid exchange introducer catheter that was used to deliver the filter assembly or an alternate introducer catheter of similar design but of a slightly larger diameter of the distal introducer to account for the embolic debris that has been collected during the interventional procedure.
Still yet another embodiment of the present invention has the distal introducer attached to the distal portion of an angioplasty catheter or other interventional catheter. In this embodiment the angioplasty catheter serves as an interventional therapeutic catheter and as an introducer catheter for the filter assembly. The angioplasty catheter can be a concentric design or a dual lumen construction design and the angioplasty catheter can be an over-the-wire design or a rapid exchange design. For example, the angioplasty catheter can have a guidewire tubing with a guidewire lumen for passage of a guidewire and an inflation lumen to inflate the dilatation balloon with contrast medium. Located distally to the dilatation balloon and attached to the guidewire tubing is located the distal introducer that was described in the previous embodiments. The distal introducer can be contiguous with the guidewire tube or it can be a separate tube which has been attached or bonded. This distal introducer contains the filter assembly. The guidewire of the present invention extends through the guidewire lumen of the angioplasty catheter and extends further distally through the filter assembly located in the distal introducer. Typical use of the device could include loading the guidewire of the present invention into the angioplasty catheter and distal introducer and advancing the guidewire and the angioplasty catheter with the distal introducer percutaneously into the vasculature. In the case of a coronary angioplasty or coronary stent placement, the angioplasty catheter with the distal introducer could be advanced within the guide catheter to the coronary ostium. In the case of carotid angioplasty or carotid stent placement, the angioplasty catheter with distal introducer could be advanced to the aortic arch or to the carotid ostium. The guidewire of the present invention is then advanced across the lesion to a site distal to the lesion. The angioplasty catheter with distal introducer is then advanced over the guidewire to a site distal to the vascular lesion. The guidewire can then be retracted to latch the ferrule or locking mechanism of the guidewire with the ejector latch of the filter assembly. Alternately the angioplasty catheter with distal introducer can be advanced distally while maintaining the position of the guidewire until the filter assembly has been latched. While maintaining the position of the guidewire the angioplasty catheter with distal introducer is withdrawn proximally a small distance to eject the filter assembly from the distal introducer and into the vessel. The filter assembly expands to form a seal with the vessel wall. The filter assembly can either remain latched to the guidewire or it can be designed to release from the guidewire allowing the guidewire to be moved distally while maintaining the position of the filter assembly within the blood vessel. The angioplasty catheter is then further withdrawn proximally until the dilatation balloon is positioned over the lesion and balloon dilatation of the lesion can proceed. If a stent is also located on the dilatation balloon, the stent can be implanted during the dilatation procedure. Following the angioplasty or other therapeutic procedure, the angioplasty catheter with distal introducer can be advanced distally a small distance and the guidewire can be retracted distally. The ferrule or locking mechanism on the guidewire will interface with the filter stop of the filter assembly and allow the filter assembly to be withdrawn back into the distal introducer. Embolic material generated by the angioplasty procedure or during stent placement will be collected in the filter assembly and will be held by the filter material of the filter assembly as it is withdrawn into the distal introducer. The angioplasty catheter with distal introducer along with the guidewire and filter assembly can then be removed from the blood vessel. It is to be understood that if an additional therapeutic or diagnostic catheter is needed following the initial angioplasty procedure, such as introducing another catheter for stent implantation, the angioplasty catheter with distal introducer can be removed while leaving the guidewire and filter assembly in place distal to the lesion. The additional therapeutic or diagnostic procedure can then be performed using the guidewire of the present invention that has been left in place and using the filter assembly that is also in place and fully deployed. Following the completion of the therapeutic or diagnostic procedure, the angioplasty catheter with distal introducer or another introducer catheter of present invention as was already described in a previous embodiment, can be used to retrieve the filter assembly by simply withdrawing the guidewire proximally into the distal introducer and pulling the filter assembly into the distal introducer. For those cases where only angioplasty is anticipated but it is desired to provide distal protection against embolic debris, this embodiment allows several benefits. First, a guidewire of standard flexibility, steerability, and trackability is first used to access the site of the lesion; the guidewire of the present invention does not have the filter assembly attached. Second, only one catheter is needed to both deliver the filter assembly and to perform the angioplasty procedure. Third, the same angioplasty catheter with distal introducer can then remove the filter assembly.